Gas turbine engine blade containment using wire wrapping

ABSTRACT

A blade containment of a gas turbine engine comprises a casing defining an annular wall radially spaced from and immediately surrounding a plurality of blades radially extending from a rotor, and at least one layer of metal wires wrapped around and directly attached to the annular wall.

TECHNICAL FIELD

The invention relates generally to gas turbine engines and, more particularly, to an improved blade containment assembly for use in gas turbine engines.

BACKGROUND OF THE ART

Turbofan gas turbine engines for powering aircraft conventionally comprise a core engine which drives a fan. The fan includes a plurality of fan blades radially extending from a fan rotor and surrounded by a generally cylindrical or truncated conical fan casing. The fan casing functions not only as an outer boundary of an annular passage for directing air flow to pass through and be driven by the fan blades, but also as a containment to prevent any broken-off fan fragments from breaking through the engine casing when a failure of the fan blades occurs in order to avoid serious consequences to the aircraft itself. Fan blade containment has been conventionally accomplished using many different techniques such as thick walled aluminium casings, thick walled steel casings, or thinner walled steel or aluminium casings with additional containment reinforcing apparatus around the casing, for example, an additional protective ring of metal plate, a number of layers of corrugated steel metal rings or a combination of metal bands and polymer-bonded fiber webbing layers. However, these conventional blade containment techniques involve either configurations with a significant weight penalty or polymer-bonded fiber web layers which disadvantageously absorb moisture and thus degrade severely under stress and which must also be protected from abrasion or cutting during handling.

Accordingly, there is a need to provide an improved blade containment assembly for gas turbine engines.

SUMMARY OF THE INVENTION

In one aspect, the present invention provides a blade containment assembly of a gas turbine engine which comprises a casing defining an annular wall radially spaced from and immediately surrounding a plurality of blades radially extending from a rotor, and at least one layer of metal wires wrapped around and directly attached to the annular wall.

In another aspect, the present invention provides a gas turbine engine which comprises at least a compressor assembly, a gas generation assembly, a turbine assembly and a fan assembly, the fan assembly including a fan rotor having a plurality of radially extending blades, and a casing defining an annular wall immediately surrounding the blades with a clearance therebetween, the annular wall including a means for reinforcing fan blade containment of the fan assembly, said means being attached directly to an outer surface of the annular wall.

In a further aspect, a method for reinforcing containment of a plurality of fan blades of a gas turbine engine comprises wrapping an annular wall of a fan casing with at least one metal wire to allow the wire to be attached directly to an outer surface of the annular wall, thereby forming at least one containment reinforcing layer and affixing the at least one containment reinforcing layer to the annular wall.

Further details of these and other aspects of the present invention will be apparent from the detailed description and drawings included below.

DESCRIPTION OF TUE DRAWINGS

Reference is now made to the accompanying figures depicting aspects of the present invention, in which.

FIG. 1 is schematic illustration of a turbofan gas turbine engine as an exemplary application of the present invention;

FIG. 2 is a partial cross-sectional view of the gas turbine engine of FIG. 1, showing a wrapping of metal wires attached to and surrounding a fan casing according to one embodiment of the present invention; and

FIG. 3 is a partial cross-sectional view of the gas turbine engine of FIG. 1, showing a wrapping of metal wires attached to and surrounding a fan casing according to another embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates an exemplary turbofan gas turbine engine 10 which includes an outer casing 28, a core casing 30, a low pressure spool assembly seen generally at 12 which includes a fan assembly 14 and a low pressure turbine assembly 18 and a high pressure spool assembly seen generally at 20 which includes a high pressure compressor assembly 22 and a high pressure turbine assembly 24. The core casing 30 surrounds the low and high pressure spool assemblies 12 and 20 in order to define a main fluid path (not indicated) therethrough, which includes a combustor 26 to form a gas generation assembly (not indicated).

Referring to FIGS. 1-3, the fan assembly 14 includes a fan rotor 32 which may be cylindrical or truncated conical and is mounted to a shaft 34 of the low pressure spool assembly 12. A plurality of fan blades 36 are mounted to the fan rotor 32 and extend radially outwardly therefrom. A fan casing 38 is provided to define an annular wall 40 radially spaced apart from and immediately surrounding the fan blades 36 in order to ensure a clearance between the annular wall 40 and the tips of the respective fan blades 36. The fan casing 38 may be part of, and thus supported by, the engine outer casing 28. A nose cone 42 is attached to a leading side of the fan rotor 32 or the front end of the shaft 34. Therefore, an air flow is introduced into an annular fluid path (not indicated) defined between the annular wall 40 of the fan casing 38 and the fan rotor 32 with the attached nose cone 42. The introduced air flow is compressed by the fan blades 36 to pass through the fan assembly 14 and is then divided by a flow splitter 44 formed at the front end of the core casing 30, into an annular bypass passage (not indicated) defined between the outer casing 28 and the core casing 30 and into the main fluid path within the core casing 30.

The annular wall 40 of the fan casing 38 functions not only as an outer ducting boundary for ducting the air flow to pass through the fan blades but also functions as a fan blade containment to prevent any detached fan segments, when a failure of the fan assembly 14 occurs, from flying to damage the aircraft on which the engine 10 is mounted. In accordance with one embodiment of the present invention, the annular wall 40 of the fan casing 38 further includes a means for reinforcing fan blade containment of the fan assembly 14. The means may include metal wires 46 attached directly to and surrounding an outer surface of the annular wall 40 to form at least one, or more layers of wrapping therearound.

The metal wires 46 may be made of steel or any other alloy material having suitable tensile strength. In the case of steel wires, the tensile strength of the steel wires which may be selected from those widely used in automobile tire manufacturing industry for “steel belted” radial tires, exceeds that of synthetic fibers such as Kevlar (a registered trademark). The metal wires 46 may be used to surround the outer surface of the annular wall 40 of the fan casing 38 in a continuous and helical pattern to form at least one or more containment reinforcing layers, as shown in FIG. 3 according to one embodiment of the invention. In this simple circumferential wrapping pattern the metal wires 46 extend substantially in the same circumferential direction. A single wire may be used to form the wrapping of one or more layers, however more sections of wires 46 may be used to form the wrapping particularly in multiple layers.

Alternatively, a plurality of steel wire sections may be used to surround the outer surface of the annular wall 40 of the fan casing 38 in a braided pattern to form at least one or more containment reinforcing layers according to a different embodiment, as shown in FIG. 2. The braided layer of metal wires 46 may be formed during a process of wrapping the metal wires 46 around the outer surface of the annular wall 40 of the fan casing 38, or may be formed by wrapping a pre-formed web of braided metal wires 46 around the outer surface of the annular wall 40 of the fan casing 38.

After the one or more layers of wrapped metal wires 46 are applied around the annular wall 40, the wires 46 are to be affixed to the annular wall 40, for example by a brazing process. Optionally, the wrapping of the metal wires 46 may be otherwise affixed to the annular wall 40 so as to allow flexibility of the metal wires 46 for thermal expansion during engine operation. For example, the metal wires 46 may be epoxied, taped or foil wrapped in place.

The wrapped metal wires 46 may cover the entire outer surface of the annular wall 40 of the fan casing 38 or may cover only an axial section of the annular wall 40 of the fan casing 38 to substantially overlap the axial position of the fan blades 36, as shown in FIG. 2. The axial section of the annular wall 40 of the fan casing 38 covered by the wrapped metal wires 46 may have an axial length greater than the tip width of the fan blades 36.

The fan casing 38 may have mounting flanges 48 radially extending from respective front and rear ends of the fan casing 38 (only one at the front end is shown) for connection with other casing parts of the outer casing 28 of the engine. Additionally, there may be provided two flanges 50 and 52 which extend radially and outwardly from the outer surface of the annular wall 40 of the fan casing 38 and are axially spaced apart from each other to define therebetween an axial section (not indicated) of the annular wall. This axial section defined between the flanges 50 and 52 substantially overlaps the tip width of the fan blades 36. Therefore, the wrapped metal wire 46 can be conveniently positioned in place to cover the entire section between the two flanges 50 and 52. The additional flanges 50 and 52 further provide rigidity and stability to the fan casing 38, given that the diametric dimension of the fan casing 38 is relatively large and the annular wall 40 of the fan casing 38 is relatively thin, in particular when the thickness of the annular wall 40 of the fan casing 38 may be further reduced due to the merit of the reinforced fan blade containment, by the wrapped metal wires 46, in order to reduce the weight of the engine.

The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departure from the scope of the invention disclosed. For example, the blade containment assembly according to the present invention may be used for other rotors such as compressor or turbine assemblies of a gas turbine engine. Still other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims. 

1. A blade containment assembly of a gas turbine engine, comprising: a casing defining an annular wall radially spaced from and immediately surrounding a plurality of blades radially extending from a rotor; and at least one layer of metal wires wrapped around and directly attached to the annular wall.
 2. The blade containment assembly as defined in claim 1 wherein the metal wires are made of steel.
 3. The blade containment assembly as defined in claim 1 wherein the metal wires form a simple circumferential wrap in which the metal wires extend substantially in a circumferential direction.
 4. The blade containment assembly as defined in claim 3 wherein the metal wires are continuous sections of a single metal wire.
 5. The blade containment assembly as defined in claim 1 wherein the metal wires form a wrap with a braided pattern.
 6. The blade containment assembly as defined in claim 1 wherein the metal wires form a plurality of layers of wrapping.
 7. The blade containment assembly as defined in claim 1 wherein the at least one layer of metal wires is brazed to an outer surface of the annular wall.
 8. The blade containment assembly as defined in claim 1 wherein the at least one layer of metal wires is attached to an outer surface of the annular wall so as to allow flexibility of the metal wires for thermal expansion during engine operation.
 9. The blade containment assembly as defined in claim 1 wherein the casing comprises two flanges extending radially and outwardly from an outer surface of the annular wall and axially spaced apart from each other to define therebetween an axial section of the annular wall, the axial section having an axial dimension substantially overlapping a tip width of the blades, the at least one layer of wrapped metal wires substantially covering the axial section between the two flanges.
 10. A gas turbine engine comprising at least a compressor assembly, a gas generation assembly, a turbine assembly and a fan assembly, the fan assembly including a fan rotor having a plurality of radially extending blades, and a casing defining an annular wall immediately surrounding the blades with a clearance therebetween, the annular wall including a means for reinforcing fan blade containment of the fan assembly, said means being attached directly to an outer surface of the annular wall.
 11. The gas turbine engine as defined in claim 10 wherein the means comprises metal wires attached to and surrounding the outer surface of the annular wall.
 12. The gas turbine engine as defined in claim 11 wherein the metal wires comprise at least one layer of steel wires.
 13. The gas turbine engine as defined in claim 11 wherein the metal wires form a wrapping substantially overlapping an axial position of the blades of the fan assembly.
 14. The gas turbine engine as defined in claim 13 wherein the wrapping substantially covers an axial length greater than a tip width of the blades.
 15. A method for reinforcing containment of a plurality of fan blades of a gas turbine engine, comprising: wrapping an annular wall of a fan casing with at least one metal wire to allow the wire to be attached directly to an outer surface of the annular wall, thereby forming at least one containment reinforcing layer; and affixing the at least one containment reinforcing layer to the annular wall.
 16. The method as defined in claim 15 wherein a steel wire is used to surround the outer surface of the annular wall in a continuous and helical pattern to form the at least one containment reinforcing layer.
 17. The method as defined in claim 15 wherein a plurality of steel wire sections are used to surround the outer surface of the annular wall in a braided pattern to form the at least one containment reinforcing layer.
 18. The method as defined in claim 15 wherein the at least one containment reinforcing layer is brazed to the annular wall.
 19. The method as defined in claim 15 wherein the at least one containment reinforcing layer is attached to the annular wall so as to allow flexibility of the at least one metal wire for thermal expansion during engine operation 